1. Field of the Invention
The present invention relates to a product, a material, and the like, including a body and a conductor filling a hole defined in the body. In particular, the present invention relates to a printed wiring board employing the product.
2. Description of the Prior Art
Consideration is given to formation of a so-called through hole in a small-sized package printed wiring board. The through hole of the small-sized printed wiring board has a larger aspect ratio and a smaller inside diameter as compared with the through hole of a general large-sized printed wiring board. The inside of the through hole must be filled up with a conductor so as to avoid a larger increase in the electric resistance of the through hole.
A through hole can be filled with a solder alloy as described in Japanese Patent Application Publication No. 2002-43751. However, since the melting point of the solder alloy is relatively low, the solder alloy unintentionally melts at a later stage where the package printed wiring board is to be mounted on a printed circuit board, for example. The molten solder alloy is likely to flow out of the through hole in this case. A thorough hole can also be filled with an electrically-conductive paste as described in Japanese Patent Application Publication No. 2003-110243. However, the electrically-conductive paste cannot flow into a through hole having the aspect ratio of 2 approximately or larger. Electroless copper plating can also be utilized to fill the through hole, for example. However, the electroless copper plating suffers from a longer operating time for filling the minute through holes. This leads to a lower production efficiency.